var FCS_16_TAB = [
    0x0000,0x1189,0x2312,0x329B,0x4624,0x57AD,0x6536,0x74BF,0x8C48,0x9DC1,0xAF5A,0xBED3,0xCA6C,
    0xDBE5,0xE97E,0xF8F7,0x1081,0x0108,0x3393,0x221A,0x56A5,0x472C,0x75B7,0x643E,0x9CC9,0x8D40,
    0xBFDB,0xAE52,0xDAED,0xCB64,0xF9FF,0xE876,0x2102,0x308B,0x0210,0x1399,0x6726,0x76AF,0x4434,
    0x55BD,0xAD4A,0xBCC3,0x8E58,0x9FD1,0xEB6E,0xFAE7,0xC87C,0xD9F5,0x3183,0x200A,0x1291,0x0318,
    0x77A7,0x662E,0x54B5,0x453C,0xBDCB,0xAC42,0x9ED9,0x8F50,0xFBEF,0xEA66,0xD8FD,0xC974,0x4204,
    0x538D,0x6116,0x709F,0x0420,0x15A9,0x2732,0x36BB,0xCE4C,0xDFC5,0xED5E,0xFCD7,0x8868,0x99E1,
    0xAB7A,0xBAF3,0x5285,0x430C,0x7197,0x601E,0x14A1,0x0528,0x37B3,0x263A,0xDECD,0xCF44,0xFDDF,
    0xEC56,0x98E9,0x8960,0xBBFB,0xAA72,0x6306,0x728F,0x4014,0x519D,0x2522,0x34AB,0x0630,0x17B9,
    0xEF4E,0xFEC7,0xCC5C,0xDDD5,0xA96A,0xB8E3,0x8A78,0x9BF1,0x7387,0x620E,0x5095,0x411C,0x35A3,
    0x242A,0x16B1,0x0738,0xFFCF,0xEE46,0xDCDD,0xCD54,0xB9EB,0xA862,0x9AF9,0x8B70,0x8408,0x9581,
    0xA71A,0xB693,0xC22C,0xD3A5,0xE13E,0xF0B7,0x0840,0x19C9,0x2B52,0x3ADB,0x4E64,0x5FED,0x6D76,
    0x7CFF,0x9489,0x8500,0xB79B,0xA612,0xD2AD,0xC324,0xF1BF,0xE036,0x18C1,0x0948,0x3BD3,0x2A5A,
    0x5EE5,0x4F6C,0x7DF7,0x6C7E,0xA50A,0xB483,0x8618,0x9791,0xE32E,0xF2A7,0xC03C,0xD1B5,0x2942,
    0x38CB,0x0A50,0x1BD9,0x6F66,0x7EEF,0x4C74,0x5DFD,0xB58B,0xA402,0x9699,0x8710,0xF3AF,0xE226,
    0xD0BD,0xC134,0x39C3,0x284A,0x1AD1,0x0B58,0x7FE7,0x6E6E,0x5CF5,0x4D7C,0xC60C,0xD785,0xE51E,
    0xF497,0x8028,0x91A1,0xA33A,0xB2B3,0x4A44,0x5BCD,0x6956,0x78DF,0x0C60,0x1DE9,0x2F72,0x3EFB,
    0xD68D,0xC704,0xF59F,0xE416,0x90A9,0x8120,0xB3BB,0xA232,0x5AC5,0x4B4C,0x79D7,0x685E,0x1CE1,
    0x0D68,0x3FF3,0x2E7A,0xE70E,0xF687,0xC41C,0xD595,0xA12A,0xB0A3,0x8238,0x93B1,0x6B46,0x7ACF,
    0x4854,0x59DD,0x2D62,0x3CEB,0x0E70,0x1FF9,0xF78F,0xE606,0xD49D,0xC514,0xB1AB,0xA022,0x92B9,
    0x8330,0x7BC7,0x6A4E,0x58D5,0x495C,0x3DE3,0x2C6A,0x1EF1,0x0F78
];

function fcs16Add(fcs,c) {
    // 'fcs' should be initialized to 0xFFFF and after the computation it should be complemented (inverted).
    // If the FCS-16 is calculated over the data and over the complemented FCS-16,
    // the result will always be 0xF0B8 (without the complementation).
    return FCS_16_TAB[(fcs^c)&0xFF]^((fcs>>8)&0xFF);
};

function fcs16(buffer){
	var fcs = 0xFFFF;

	for(var i = 0, len = buffer.length; i < len; i++) {
	    fcs = fcs16Add(fcs, buffer[i]);
	}

	return fcs^0xFFFF;
};

exports.crc16 = fcs16;
